Whatever the name, these wingtip extensions have become prevalent in recent years and have saved airlines billions of dollars in fuel costs. The newest, and funkiest-looking, version was used on a United Airlines commercial flight for the first time last month. The new design features the upturned wingtip but adds a downward-facing sword and sinister-looking pointed tips, which together make it a "split scimitar winglet."

Winglets might look cool and represent one of the more radical changes to the appearance of modern jets, but in truth, they're all business.

While winglets could cost $1 million or more per aircraft to install and add several hundred pounds to an aircraft, they pay for themselves in a few years through fuel savings — about 4 percent savings for the blended winglet and an additional 2 percent savings for the split scimitar.

For airlines, adding the 8-foot-tall blended winglets has become a no-brainer, and adding the split scimitar version also seems to be.

"We have the philosophy: Put them on everything that we can," said Ron Baur, fleet vice president at Chicago-based United Airlines. "Anything we can do to save fuel, we're all over it. They're a huge deal for us."

Winglets reduce drag and increase lift at the end of the wings, where the physics of flight create small tornadoes. Winglets essentially reduce the size of those whirling air masses and improve the plane's "gas mileage" by helping jets more efficiently slice through the sky.

Savings of 4 percent and 2 percent might not sound like much, but consider that United uses 4 billion gallons of fuel in a year, or 1 percent of the world's annual oil supply. And consider that jet fuel prices have soared during the past 15 years, from about 50 cents per gallon to $3 per gallon today.

A single set of scimitar winglets on one plane at United saves about 45,000 gallons of jet fuel in a year, the airline said. For perspective, that's as many gallons of gasoline as an average car would use in 72 years.

United expects the new and older wingtip designs on its 737, 757 and 767 fleets to annually save it 65 million gallons of fuel, $200 million worth, and the equivalent of 645,000 metric tons of carbon dioxide emissions.

"Fuel is our biggest expense and our most volatile expense," Baur said. "Anything that has a savings due to fuel efficiency is one of our top priorities."

A different case in point: United's new Boeing 737s have slightly modified anti-collision lights that reduce drag and improve fuel efficiency by just a few tenths of a percent.

"We chase very small percentages," Baur said.

That why winglets are suddenly so important, and why airlines have been rushing to order winglets on new planes and add them to existing aircraft.

About 7,000 blended winglet systems have been sold, the majority of which are in service with more than 200 airlines in more than 100 countries, according to Aviation Partners Boeing, a Seattle-based Boeing joint-venture company that sells the winglets for Boeing aircraft.

Last fall, Southwest Airlines touted its winglets in an ad campaign, calling them "doo-hickeys" and noting they save the airline 54 million gallons of fuel each year and reduce emissions. The airline says it's one way it is trying to keep fares low.

The version of winglets for Airbus planes, called sharklets, have been available relatively recently as a retrofit for existing aircraft, but they will be a standard feature on the latest A320neo series, due to start flying in 2015.

Perhaps not surprising because Airbus and Boeing are bitter rivals in the aircraft sales business, Airbus and Aviation Partners Boeing are in a patent dispute about the wingtips.

Another beneficiary of the winglet craze is AAR Corp., headquartered in Wood Dale, Ill., near O'Hare International Airport. It is among the aviation maintenance companies installing winglets on existing aircraft.

Business has been booming.

AAR has installed blended winglets on about 250 aircraft in recent years and will start installing the split scimitar winglets this month, said Chris Jessup, AAR senior vice president of airframe and engineering services.

"They're very popular," he said. "It's additional work, above and beyond the normal work that we do."

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